Thin film transistor, method for fabricating the same, array substrate, and display panel

ABSTRACT

A thin film transistor, a method for fabricating the same, an array substrate, and a display panel are disclosed. The method includes: forming a semiconductor film comprising metallic elements, an etching stop film, and a source and drain film on a substrate in this order; and forming a pattern comprising an active layer, an etching stop layer, and a source and drain on the active layer by using a same mask plate, wherein the etching stop layer electrically connects the source and drain with the active layer. Since an etching stop film is formed on a semiconductor film comprising metallic elements, during etching the metal layer, the etching stop film can protect the semiconductor film comprising metallic elements from being etched, and this ensures the performance of the resultant active layer.

RELATED APPLICATIONS

The present application is the U.S. national phase entry ofPCT/CN2017/106504, with an international filing date of Oct. 17, 2017,which claims the benefit of Chinese Patent Application No.201610943113.4, filed on Oct. 31, 2016, the entire disclosures of whichare incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the field of display technologies, andparticularly to a thin film transistor, a method for fabricating thesame, an array substrate, and a display panel.

BACKGROUND

A thin film transistor (TFT) plays a key role in a display device. As anon-linear switching element, the thin film transistor has been widelyapplied to a large size LCD display and AM-OLED display.

An active layer of the thin film transistor may be a semiconductormaterial comprising metallic elements, for example a metal oxidesemiconductor material, or a metal-doped semiconductor material. In thiscase, during etching a metal layer to form a source and a drain, sincethe active layer comprises metallic elements, this etching will damagethe active layer region between the source and the drain. This resultsin that the design requirements cannot be met, the mobility is reduced,and the performance of thin film transistor is affected.

SUMMARY

Embodiments of the present disclosure provides a thin film transistor, amethod for fabricating the same, an array substrate, and a displaypanel, which alleviates or overcomes one or more of the above defects.

In a first aspect, the present disclosure provides a method forfabricating a thin film transistor, comprising:

forming a semiconductor film comprising metallic elements, an etchingstop film, and a source and drain film on a substrate in this order; and

forming a pattern comprising an active layer, an etching stop layer, anda source and drain on the active layer by using a same mask plate,wherein the etching stop layer electrically connects the source anddrain with the active layer.

For example, forming the pattern comprising the active layer, theetching stop layer, and the source and drain on the active layer byusing a same mask plate comprises:

coating a photoresist layer on the source and drain film;

exposing and developing the photoresist layer by using a gray tone maskplate, to form a first photoresist completely retained region in aregion corresponding to a pattern of source to be formed, forming asecond photoresist completely retained region in a region correspondingto a pattern of drain to be formed, forming a photoresist partiallyretained region in a region between the region corresponding to thepattern of source to be formed and the region corresponding to thepattern of drain to be formed, and forming a photoresist completelyremoved region surrounding the region corresponding to a pattern ofactive layer to be formed; and

etching the source and drain film, the etching stop film, and thesemiconductor film comprising metallic elements by using the photoresistlayer, to form a pattern comprising the source, the drain, and theactive layer.

For example, etching the source and drain film, the etching stop film,and the semiconductor film comprising metallic elements by using thephotoresist layer to form the pattern comprising the source, the drainand the active layer comprises:

wet etching the source and drain film for a first time, to retain thesource and drain film in a region corresponding to the first photoresistcompletely retained region, the second photoresist completely retainedregion, and the photoresist partially retained;

dry etching the etching stop film for a first time, to retain theetching stop film in a region corresponding to the first photoresistcompletely retained region, the second photoresist completely retainedregion, and the photoresist partially retained;

ashing the photoresist layer in the first photoresist completelyretained region, the second photoresist completely retained region, andthe photoresist partially retained region, to completely remove thephotoresist layer in the photoresist partially retained region, and thinthe photoresist layer in the first photoresist completely retainedregion and the second photoresist completely retained region;

wet etching the source and drain film for a second time, to retain thesource and drain film in a region corresponding to the first photoresistcompletely retained region and the second photoresist completelyretained region, so as to form a pattern comprising source and drain;

wet etching the semiconductor film comprising metallic elements, toretain the semiconductor film comprising metallic elements in a regioncorresponding to the first photoresist completely retained region, thesecond photoresist completely retained region, and the photoresistpartially retained region, so as to form a pattern comprising activelayer;

dry etching the etching stop film for a second time, to remove theetching stop film in a region corresponding to the photoresist partiallyretained region; and

removing the photoresist layer in the first photoresist completelyretained region and the second photoresist completely retained region.

For example, prior to forming the semiconductor film comprising metallicelements, the etching stop film, and the source and drain film on thesubstrate in this order, the method further comprises: forming a patterncomprising gate and a gate insulating layer covering the patterncomprising gate on the substrate, and

wherein forming the semiconductor film comprising metallic elements, theetching stop film, and the source and drain film on the substrate inthis order, comprises: forming the semiconductor film comprisingmetallic elements, the etching stop film, and the source and drain filmon the substrate on which the pattern comprising gate and the gateinsulating layer have been formed.

For example, the semiconductor film comprising metallic elementscomprises a metal oxide semiconductor material or a metal-dopedsemiconductor material.

For example, the etching stop film comprises graphite, graphene, or acarbon nanomaterial. For example, the etching stop film comprises amixture of a non-metal oxide and at least one of graphite, graphene, anda carbon nanomaterial. For example, the etching stop film comprises anon-metal dopant.

For example, the etching stop film has a thickness of about 800 Å˜3000Å.

In a second aspect, the present disclosure provides a thin filmtransistor, comprising a substrate, a semiconductor active layercomprising metallic elements on the substrate, a source and drain on theactive layer, and an etching stop layer between the source and theactive layer and between the drain and the active layer, wherein theetching stop layer electrically connects the source and drain with theactive layer.

In a third aspect, the present disclosure provides an array substrate,comprising the thin film transistor as described above.

In fourth aspect, the present disclosure provides a display device,comprising the array substrate as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view for illustrating a thin film transistor;

FIG. 2 is a flow chart for illustrating a method for fabricating a thinfilm transistor in an embodiment of the present disclosure;

FIG. 3 is a structural view for illustrating a thin film transistor inan embodiment of the present disclosure; and

FIGS. 4a, 4b, 4c, 4d, 4e, 4f, 4g and 4h are structural views forillustrating a thin film transistor during fabricating process in anembodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

A thin film transistor, a method for fabricating the same, an arraysubstrate, and a display panel in embodiments of the present disclosurewill be described in detail hereinafter with reference to theaccompanying drawings and specific implementations.

Currently, as shown in FIG. 1, a conventional thin film transistor of abottom gate type comprises a substrate 1, a gate 2 on the substrate 1,an active layer 4 insulated from the gate 2 by an insulating layer 3, asource 5 and a drain 6 which are electrically connected with the activelayer 4. As for the thin film transistor in which the active layer 4 isformed by a semiconductor material comprising metallic elements, duringetching a metal layer to form the source 5 and the drain 6, since theactive layer 4 also comprises metallic elements, such an etching willdamage the active layer region between the source 5 and the drain 6.This results in that the design requirements cannot be met, the mobilityis reduced, and the performance of thin film transistor is affected.

In an embodiment of the present disclosure, a method for fabricating athin film transistor is provided. As shown in FIG. 2, the methodcomprises the following steps:

step 210, forming a semiconductor film comprising metallic elements, anetching stop film, and a source and drain film on a substrate in thisorder; and

step 220, forming a pattern comprising an active layer, an etching stoplayer, and a source and drain on the active layer by using a same maskplate, wherein the etching stop layer electrically connects the sourceand drain with the active layer.

The etching stop film can protect the semiconductor film comprisingmetallic elements during etching the metal layer. Since the etching stopfilm is formed on the semiconductor film comprising metallic elements,during a patterning process, the etching stop film protects thesemiconductor film comprising metallic elements from being etched, thusensuring the performance of the resultant active layer.

Besides, the method for etching the etching stop film is different fromthe method for etching the semiconductor film comprising metallicelements, so that there is no damage to the semiconductor filmcomprising metallic elements.

Furthermore, in the present method, the pattern comprising the source,the drain, the etching stop layer and the active layer is formed byetching only by using a same mask plate. This decreases the maskingtimes, simplifies the process, and reduces the cost.

In implementations, for example, the step 220 comprises the followingsteps:

coating a photoresist layer on the source and drain film;

exposing and developing the photoresist layer by using a gray tone maskplate, to form a first photoresist completely retained region in aregion corresponding to a pattern of source to be formed, forming asecond photoresist completely retained region in a region correspondingto a pattern of drain to be formed, forming a photoresist partiallyretained region in a region between the region corresponding to thepattern of source to be formed and the region corresponding to thepattern of drain to be formed, and forming a photoresist completelyremoved region surrounding the region corresponding to a pattern ofactive layer to be formed; and

etching the source and drain film, the etching stop film, and thesemiconductor film comprising metallic elements by using the photoresistlayer, to form a pattern comprising the source, the drain, and theactive layer.

In this embodiment, a gray tone mask plate is used to form a mask. Inimplementations, a half tone mask plate can be used to form a mask.

In implementations, for example, etching the source and drain film, theetching stop film, and the semiconductor film comprising metallicelements by using the photoresist layer to form the pattern comprisingthe source, the drain and the active layer comprises:

wet etching the source and drain film for a first time, to retain thesource and drain film in a region corresponding to the first photoresistcompletely retained region, the second photoresist completely retainedregion, and the photoresist partially retained;

dry etching the etching stop film for a first time, to retain theetching stop film in a region corresponding to the first photoresistcompletely retained region, the second photoresist completely retainedregion, and the photoresist partially retained; ashing the photoresistlayer in the first photoresist completely retained region, the secondphotoresist completely retained region, and the photoresist partiallyretained region, to completely remove the photoresist layer in thephotoresist partially retained region, and thin the photoresist layer inthe first photoresist completely retained region and the secondphotoresist completely retained region;

wet etching the source and drain film for a second time, to retain thesource and drain film in a region corresponding to the first photoresistcompletely retained region and the second photoresist completelyretained region, so as to form a pattern comprising source and drain;

wet etching the semiconductor film comprising metallic elements, toretain the semiconductor film comprising metallic elements in a regioncorresponding to the first photoresist completely retained region, thesecond photoresist completely retained region, and the photoresistpartially retained region, so as to form a pattern comprising activelayer;

dry etching the etching stop film for a second time, to remove theetching stop film in a region corresponding to the photoresist partiallyretained region; and

removing the photoresist layer in the first photoresist completelyretained region and the second photoresist completely retained region.

In this embodiment, during etching the source and drain film by wetetching, the etching stop film can protect the semiconductor filmcomprising metallic elements from being etched. The etching stop film isetched by dry etching. Generally the dry etching will not damage to thesemiconductor film comprising metallic elements. This further ensuresthe performance of the resultant active layer.

In the above embodiments, the photoresist can be a positive photoresist,or a negative photoresist.

On basis of any one of the above embodiments, for example, prior toforming the semiconductor film comprising metallic elements, the etchingstop film, and the source and drain film on the substrate in this order,the method further comprises: forming a pattern comprising gate and agate insulating layer covering the pattern comprising gate on thesubstrate.

Forming the semiconductor film comprising metallic elements, the etchingstop film, and the source and drain film on the substrate in this order,comprises: forming the semiconductor film comprising metallic elements,the etching stop film, and the source and drain film on the substrate onwhich the pattern comprising gate and the gate insulating layer havebeen formed.

On basis of any one of the above embodiments, for example, thesemiconductor film comprising metallic elements can comprise, but notlimited to, a metal oxide semiconductor material or a metal-dopedsemiconductor material.

The metal oxide semiconductor material can be, but not limited to, IGZO.

metal-doped semiconductor material can be, but not limited to, zincsulfide (ZnS), cadmium telluride (CdTe), copper gallium selenide(CuGaSe₂), silver indium telluride (AgInTe₂), silver thallium telluride(AgTlTe₂), or copper iron tin sulphide (Cu₂FeSnS₄).

On basis of any one of the above embodiments, for example, the etchingstop film can comprise, but not limited to, graphite, graphene, a carbonnanomaterial; a mixture of a non-metal oxide and at least one ofgraphite, graphene, and a carbon nanomaterial; or a non-metal dopant.These materials are only some examples for the etching stop film, andthe etching stop film can also be made from other materials, providedthat it can protect the semiconductor film comprising metallic elementsfrom being etched, and etching of the etching stop film will not damagethe semiconductor film. The etching stop film is made from anelectrically conductive material, so that the resulting etching stoplayer electrically connects the source and drain with the active layer,respectively.

The non-metal dopant can be silicon which is doped with one of boron,nitrogen, phosphorus and arsenic, germanium which is doped with one ofboron, nitrogen, phosphorus and arsenic, or other suitable materials.

The non-metal oxide can be, but not limited to, silicon oxide or siliconoxynitride.

The etching stop film has a thickness of about 800 Å˜3000 Å. Forexample, the etching stop film has a thickness of 1000 Å.

On basis of the same inventive concept, an embodiment of the presentdisclosure further provides a thin film transistor. The thin filmtransistor is fabricated by the method of any one of the aboveembodiments. The thin film transistor comprises a substrate, asemiconductor active layer comprising metallic elements on thesubstrate, a source and drain on the active layer, and an etching stoplayer between the source and the active layer and between the drain andthe active layer, wherein the etching stop layer electrically connectsthe source and drain with the active layer.

A thin film transistor and a method for fabricating the same inembodiments of the present disclosure will be described hereinafter indetail, with reference to a specific structure of the thin filmtransistor.

In this embodiment, the thin film transistor has a structure shown inFIG. 3. The thin film transistor comprises a substrate 01, a gate 02 onthe substrate 01, a gate insulating layer 03 covering the gate 02, apattern comprising active layer 04 of a metal oxide semiconductormaterial on the gate insulating layer 03, a pattern comprising source 05and a pattern comprising drain 06 on the pattern comprising active layer04, and an etching stop layer 07 between the pattern comprising source05 and the pattern comprising active layer 04 and between the patterncomprising drain 06 and the pattern comprising active layer 04. A methodfor fabricating this thin film transistor structure for examplecomprises the following step 1˜step 9.

Step 1, the gate 02, the gate insulating layer 03, a metal oxidesemiconductor film 04′, an etching stop film 07′, a source and drainfilm 05′ and a photoresist layer 08 are formed on the substrate 01 inthis order, as shown in FIG. 4 a.

In this embodiment, the etching stop film is a graphite, and the metaloxide semiconductor film comprises Indium Gallium Zinc Oxide (IGZO).

Step 2, the photoresist layer 08 is exposed and developed. In thephotoresist layer 08, a first photoresist completely retained region Ais formed in a region corresponding to a pattern of source to be formed,a second photoresist completely retained region B is formed in a regioncorresponding to the pattern of drain to be formed, a photoresistpartially retained region C is formed in a region between the regioncorresponding to the pattern of source to be formed and the regioncorresponding to the pattern of drain to be formed, and a photoresistcompletely removed region D is formed to surround the regioncorresponding to the pattern of active layer to be formed, as shown inFIG. 4 b.

Step 3, the source and drain film 05′ is etched for a first time by wetetching, and the source and drain film 05′ in regions corresponding tothe first photoresist completely retained region A, the secondphotoresist completely retained region B, and the photoresist partiallyretained region C is retained, as shown in FIG. 4 c.

Step 4, the etching stop film 07′ is etched for a first time by dryetching, and the etching stop film 07′ in regions corresponding to thefirst photoresist completely retained region A, the second photoresistcompletely retained region B, and the photoresist partially retainedregion C is retained, as shown in FIG. 4 d.

Step 5, the photoresist layer 08 in the first photoresist completelyretained region A, the second photoresist completely retained region B,and the photoresist partially retained region C is ashed, to completelyremove the photoresist layer 08 the photoresist partially retainedregion C, and at the same time, to thin the photoresist layer 08 in thefirst photoresist completely retained region A and the secondphotoresist completely retained region B, as shown in FIG. 4 e.

Step 6, the source and drain film 05′ is etched for a second time by wetetching, to remove the source and drain film 05′ in a regioncorresponding to the photoresist partially retained region C, and toretain the source and drain film 05′ in regions corresponding to thefirst photoresist completely retained region A and the secondphotoresist completely retained region B, so as to at least form thepattern comprising source 05 and the pattern comprising drain 06, asshown in FIG. 4 f.

Step 7, the metal oxide semiconductor film 04′ is etched by wet etching,to retain the metal oxide semiconductor film 04′ in regionscorresponding to the first photoresist completely retained region A, thesecond photoresist completely retained region B and photoresistpartially retained region C, so as to at least form the patterncomprising active layer 04, as shown in FIG. 4 g.

Step 8, the etching stop film 07′ is etched for a second time by dryetching, to remove the etching stop film 07′ in a region correspondingto the photoresist partially retained region C, as shown in FIG. 4 h.

In this step, the etching of the etching stop film 07′ is completed,forming the etching stop layer 07 shown in FIG. 3.

Step 9, the photoresist layer 08 in the first photoresist completelyretained region A and the second photoresist completely retained regionB is removed.

After this step, the thin film transistor with the structure shown inFIG. 3 is obtained.

On basis of the same inventive concept, an embodiment of the presentdisclosure further provides an array substrate, which comprises the thinfilm transistor in any one of the above embodiments.

On basis of the same inventive concept, an embodiment of the presentdisclosure further provides a display device, which comprises the arraysubstrate in any one of the above embodiments. It is noted that thedisplay device can be any product or component with a display function,such as a liquid crystal display panel, electronic paper, an OLED panel,a mobile phone, a tablet computer, a TV set, a monitor, a notebookcomputer, a digital photo frame, a navigator.

In the thin film transistor, the method for fabricating the same, thearray substrate, and the display panel of embodiments of the presentdisclosure, since an etching stop film is formed on a semiconductor filmcomprising metallic elements, during etching the metal layer, theetching stop film can protect the semiconductor film comprising metallicelements from being etched, and this ensures the performance of theresultant active layer.

Apparently, the person with ordinary skill in the art can make variousmodifications and variations to the present disclosure without departingfrom the spirit and the scope of the present disclosure. In this way,provided that these modifications and variations of the presentdisclosure belong to the scopes of the claims of the present disclosureand the equivalent technologies thereof, the present disclosure alsointends to encompass these modifications and variations.

1. A method for fabricating a thin film transistor, comprising: forminga semiconductor film comprising metallic elements, an etching stop film,and a source and drain film on a substrate in this order; and forming apattern comprising an active layer, an etching stop layer, and a sourceand a drain on the active layer by using a same mask plate, wherein theetching stop layer electrically connects the source and drain with theactive layer.
 2. The method of claim 1, wherein the step of forming thepattern comprising the active layer, the etching stop layer, and thesource and the drain on the active layer by using a same mask platecomprises: coating a photoresist layer on the source and drain film;exposing and developing the photoresist layer by using a gray tone maskplate, to form a first photoresist completely retained region in aregion corresponding to a pattern of source to be formed, forming asecond photoresist completely retained region in a region correspondingto a pattern of drain to be formed, forming a photoresist partiallyretained region in a region between the region corresponding to thepattern of source to be formed and the region corresponding to thepattern of drain to be formed, and forming a photoresist completelyremoved region surrounding the region corresponding to a pattern ofactive layer to be formed; and etching the source and drain film, theetching stop film, and the semiconductor film comprising metallicelements by using the photoresist layer, to form a pattern comprisingthe source, the drain, and the active layer.
 3. The method of claim 2,wherein the step of etching the source and drain film, the etching stopfilm, and the semiconductor film comprising metallic elements by usingthe photoresist layer to form the pattern comprising the source, thedrain and the active layer comprises: wet etching the source and drainfilm for a first time, to retain the source and drain film in a regioncorresponding to the first photoresist completely retained region, thesecond photoresist completely retained region, and the photoresistpartially retained; dry etching the etching stop film for a first time,to retain the etching stop film in a region corresponding to the firstphotoresist completely retained region, the second photoresistcompletely retained region, and the photoresist partially retained;ashing the photoresist layer in the first photoresist completelyretained region, the second photoresist completely retained region, andthe photoresist partially retained region, to completely remove thephotoresist layer in the photoresist partially retained region, and thinthe photoresist layer in the first photoresist completely retainedregion and the second photoresist completely retained region; wetetching the source and drain film for a second time, to retain thesource and drain film in a region corresponding to the first photoresistcompletely retained region and the second photoresist completelyretained region, so as to form a pattern comprising source and drain;wet etching the semiconductor film comprising metallic elements, toretain the semiconductor film comprising metallic elements in a regioncorresponding to the first photoresist completely retained region, thesecond photoresist completely retained region, and the photoresistpartially retained region, so as to form a pattern comprising activelayer; dry etching the etching stop film for a second time, to removethe etching stop film in a region corresponding to the photoresistpartially retained region; and removing the photoresist layer in thefirst photoresist completely retained region and the second photoresistcompletely retained region.
 4. The method of claim 1, wherein prior toforming the semiconductor film comprising metallic elements, the etchingstop film, and the source and drain film on the substrate in this order,the method further comprises: forming a pattern comprising gate and agate insulating layer covering the pattern comprising gate on thesubstrate, and wherein the step of forming the semiconductor filmcomprising metallic elements, the etching stop film, and the source anddrain film on the substrate in this order, comprises: forming thesemiconductor film comprising metallic elements, the etching stop film,and the source and drain film on the substrate on which the patterncomprising gate and the gate insulating layer have been formed.
 5. Themethod of claim 1, wherein the semiconductor film comprising metallicelements comprises a metal oxide semiconductor material or a metal-dopedsemiconductor material.
 6. The method of claim 1, wherein the etchingstop film comprises graphite, graphene, or a carbon nanomaterial.
 7. Themethod of claim 1, wherein the etching stop film comprises a mixture ofa non-metal oxide and at least one of graphite, graphene, and a carbonnanomaterial.
 8. The method of claim 1, wherein the etching stop filmcomprises a non-metal dopant.
 9. The method of claim 8, wherein thenon-metal dopant is silicon which is doped with one of boron, nitrogen,phosphorus and arsenic, or germanium which is doped with one of boron,nitrogen, phosphorus and arsenic.
 10. The method of claim 1, wherein theetching stop film has a thickness of about 800 Å˜3000 Å.
 11. A thin filmtransistor, comprising a substrate, a semiconductor active layercomprising metallic elements on the substrate, a source and drain on theactive layer, and an etching stop layer between the source and theactive layer and between the drain and the active layer, wherein theetching stop layer electrically connects the source and the drain withthe active layer.
 12. An array substrate, comprising the thin filmtransistor of claim
 11. 13. A display device, comprising the arraysubstrate of claim 12.